QSPR Analysis Of Benzenoids By Linear Regression Modeling Using The Inverse Sum In-Degree Index^*

Topological indices work as numerical molecular descriptors in quantitative structure property relationships (QSPR) models. The inverse sum in-degree index (henceforth ISI index) is a degree-based topological index, defined to design a novel descriptor in modeling molecular properties with higher accuracy than previously available descriptors. Benzenoids belong to a class of aromatic hydrocarbons containing at least one benzene ring, with several applications in household goods, electronics, healthcare, textiles, etc. From graph theoretical perspective, the formation of a chain of benzene rings can be regarded as edge fusion of cycles of length six. In this regard, a detailed study of the structure of benzenoids and their ISI index are presented. The expression and the bounds for the ISI index of benzenoids are derived in terms of the number of benzene rings present in it. Further, the predictive potential of the inverse sum in-degree index of Benzenoids is studied with the help of regression analysis. The linear regression models for the inverse sum in-degree index of benzenoids against various physicochemical and thermodynamic properties like molecular weight, complexity, density, boiling point, magnetic susceptibility, refractive index, and melting point are obtained. On the whole, the extent of the relationship between the ISI index and the physicochemical parameters of benzenoids is studied in this article.